Isomers



Patented Dec. 1931 A's-Eur p ss-m H NRY vvnrnannnivn was stream/innit; or soars IvIIIiV/AUKEE, Wiscoivsiriv, A S smNoRa YMEsNn AssIcnMENTsgro DU ron'r DE NEMOURS a COMPANY, A

' No Drawing. '1

CORPORATION; or DELAWARE sErARArIoN or ALPHA ivrono SUBSTITUTEli NAPHTHALanns rnoivt Tan a QBET'A rsoi/Iaas This invention relates to a process of puri- V tying organic bodies of thenaphthalene series and moreparticularly to a process of isolatingin substantially pure form a naphthalene derivative substituted in the alpha position I from a mixture containing besides the alpha substituted naphthalene,appreciable amounts of theisomeric beta substituted naphthalene and a small amount of other impurities- The organic bodies coming Within the scope of this invention include mono-substithylamine.

tuted naphthalenes, such as alpha and beta nitro naphthalene and alpha and beta naph- It is anob ect of this invention to provide an economically practical-method for the :preparation of substantiallypure'alpha nitro:

naphthalene and substantially pure alpha separation'in substantially pul'efor'min a nitronaphthalene andcrude alpha naphthylamine. V It is to be understood that ifthe desired. product is alpha naphthylamine, then either "the crude alpha nitro naphthalene may be- =purified to give a purified alpha nitro' mph thalene, which may be reduced to substantial- 7 ly'pure alpha naphthylamine; or the crude centrifuge or hydroextractor.

:alpha nitro naphthalene may be reduced to give a crude alpha naphthylamine, WlllCh may then be purified to the substantially pure form. o

In the use of therterm crude nitro naphthalenei and crude alpha 7 naphthylamine,

We mean to designate the crude products in the obtaining of which no attempthas been made to separate the beta isomer.

It is a Well known fact that technical alpha naphthylam'ine, contains appreciable quantities of beta nfaphthylamine; -Althou ghthe step of. fraction'ally distilling either'the crude i-tro naphthalene or the crude alpha naph v thylanline may accomplish a certain amount of purification, it has not been foundefleca tive in substantially lowering the beta content V V p v r The heretofore known methods of preparing alpha naphthylamine inasubstantially f covery of the solvent used.

' siderable' saving in cost of appueanonmea February ejieee. s ller No. 252,419.

pure form that is practically free from beta ,naphthylamine, have employedthestep of Vorystallizing' the crude alpha naphthylamine to remove the"beta bythe use of an added solvent, said solvent being of a nature which; \Vlll dissolve not only the beta; naphthylamine but also large amounts of the desired product,

alpha naphthylamine (see British Patent No; 163% of'1907). In a recent patent, namely U. S. Patent 1,581,258, thereis-de scribed a method for the purificationzofalpha nitro naphthalene by lecrystallizing; the

crude ni' ro naphthalene from organic solvents such as solvent naphtha, petroleum ether, benzene, toluene and turpentine.-

Itis to be noted, in the most recent literature on the purification of either crude alpha nitro naphthalene or crude alpha naphthyl- -s.mi11e, t-hat there is employed an added organic solvent, \vhichacts as a ready solvent;

not only for the beta isomer, but'also for the alpha isomer. The use of-such solvents results in lower yields of-the desired product.

It is to be further noted that in the above disclosed method, there are employed at least twodistinct types zefapparatus for the pu rification; namely, one type to perform .the actual crystallization and another to vremove the solvent containing the dissolved impurities, an example of the latter type being a; In addition to these twosets oiapparatus, there isalso required some form of apparatus forthe {re- Consequently, the use of a solvent and additional ap 'ajaratu s; entails certain"unnecessary steps, solvent losses and" the like which according to our presentinvention may beeliminated, Whereby We are able to etl'ect a more economical recovery of the desired product at acon g keep and 'in labor. 7 o

It is generally ,knowmthat uponjcooling a liquid system composed principally of tWo chemical isomers, each having definite melt ing pointsinthe purestatc, provided the, isomers do not crystallize in such a manner as to form mixed crystals, there results at first a crystallization of a single isomer in pure form. The crystallization of thesingle apparatus,.in upa isomer will continue upon cooling the system until a certain point is reached, known as the eutectic point. If cooling is continued below the eutectic point, the eutectic mixture will crystallize. Eutectic point is here used in the usual accepted sense as meaning the lowest temperature to which a mixture of two or more crystalline components may be cooled without effecting the crystallization of a mixture of the components. The mother liquor remaining liquid at the eutectic temperature is here referred to as the eutectic liquor. It therefore follows that at the eutectic point the eutectic liquor is incapable of dissolving any of the components of the system and has a definite composition. However, if the temperature of the system is raised above the eutectic point, the eutectic liquor then acts as a solvent for the component present in the system in crystal form.

In the system of isomers under consideration, if the liquid portion be drained off at the eutectic point, the liquid system is in such a state of equilibrium that the introduction of either of the pure isomers will raise the melting point; or conversely, the eutectic liquor, that is, the portion separated from the partially crystallized system at the eutectic temperature will not act as a solvent for either of the pure isomers at the eutectic temperature, since it is saturated with respect to both isomers at the eutectlc point. Therefore, the specific problem to elfect purification is the removal of this eutectic liquor.

The complete removal. of the eutectic liquor becomes difiicult of accomplishment at or about the eutectic point for the reason that the eutectic liquor tends strongly to adhere to the crystals and to be retained in the crystal mass by capillary action. If, however, the temperature is raised above the eutectic point, the eutectic liquor then acts as a solvent to dissolve some of the crystals and form a liquor richer in one of the components, namely the desired component. The result is that less of the desired component is obtained in crystal form but a larger proportion of the eutectic liquor can be readily drained off of the crystals.

Instead of simply draining off the eutectic liquor by gravity and displacement thereof by eutectic liquor richer in the desired component, suction may be applied or air forced through the crystal mass to displace the eutectic liquor. Water may likewise be used in place of, or in addition to air, as the displacing medium.

Furthermore, since upon cooling a system as described above there results the crystallization of a single pure isomer down to a certain point, namely the eutectic point, it appears to us therefore to be highly disadvantageous to add to the system a solvent, more particularly such solvents as are described in hitherto disclosed methods which act as ready solvents for both isomers. For by adding a solvent, there results not only a solution of the impurity but a solution of the desired product, thereby lowering the yield of the desired product.

In our process, however, the enriched liquor, after the true eutectic liquor has been largely drawn off at the eutectic point, is separately drawn of and-can be directly reused in subsequent operations, whereby loss of the desired product is largely eliminated. This is not the case where external solvents are used, since there the external solvents must be separately recovered.

It is to be noted here that the above statement-s refer strictly to ideal cases wherein there are only two constitutents or isomers, as for example, beta nitro naphthalene and alpha nitro naphthalene. However, in the manufacturing processes on a large scale, there are usually pr sent small quantities of other constituents, as for example, small amounts of naphthalene. In these cases, the above statements do not hold strictly true, but for all practical purposes may be regarded as being suiiiciently exact to bring about desirable results. Satisfactory results may nevertheless be realized, using our process, where naphthalene is present in the system in considerable amount, as where an appreciable excess of naphthalene remains in the nitration mass.

The solution of the problem of purification, therefore, resides first in the cooling of the molten mixture, say of beta naphthylamine and alpha naphthylamine, as it is usually obtained in the crude state by the reduction of crude alpha nitro naphthalene, to a 'minimum temperature under very closely regulated conditions of cooling in order to obtain the crystals of the desired product, alpha naphthylamine, in maximum amount; secondly in the obtaining of the crystals in such a physical form that the liquid impurities may be advantageously removed from the crystals; and thirdly, in re moving the liquid impurities in a practical manner.

These conditions are most advantageously met by placing the molten mass containing the desired product and the impurities to be rem ved in a tank equipped with coils set at close intervals to one another throughout the tank. Through these coils is circulated a medium, the tenn erature being controlled by a thermostat and a heating unit capable of maintaining the temperature within C. of the desired point. In order to form crystals of good physical form, it is advantageous not to agitate them during the step of crysttdhzing. The liquid impurities which gravitate to the bottom of the tank are removed by simply draining or by draining and suction. lVorking under these conditions,

' 2sattherintermdiates-aha'dyestufis.

; the 1;iq uid 'iinpuritiesi thus eliminating the d 3 fstep 'of haliidlingandoontact with' 'the'matethe desired product" isierysfialliied outwith iewerea m outreoeosbvere eiiedef about maztimiim efficiency and? the-' impurities *are '24 hours. This temperature is maintained llfor the fmostpart present in the liquid state. until equilibriilm f 1 is reached in the liquid- I The'product-"whichhas beeu sixuply drainedcrystal system. -A valve iS-then openedion 5'" of the liquidiiripuritieshasbeemf undto-be the bottom of the crystallizer and the liquid ""siiflieiehtly pure for manyuses; but-Timorder to obtain preduts'bfthe 'h'ighstipuiityfit is "fiecessary todisplace theremaining liquiCl tui'e "lIl the}coils isTthen -sloivly i-aised-fto impurities as by 's'uctioml air pressure 01' "about 5 50 C. and 'at the same time the liquea wate p v *fiedportion drained oil; When the flow has p After displacing the liquid impurities practically stopped, the valve on the bottom fromthe'crystals as outlined; -followed by "of'the crystallizer is closedand the crystals fcomplete melting and a distillation for melted;' Theialpha}nitro naphthalene thus a; cleansin purpuseg'we new fy rude alpha nitre na prepared in the laboratory, and alpha ha phtriylamin" fronrthe' "crude naphth lumine to' Example into a crystallizer, {Cooling water is run through coils in the crystallizer at an initial 1 temperature- 0f C, .Thistemperature is gradually lowered over a period of 24 hours i pared td 48'17 Ca ior very h'ighly' zpuprified materialprepared mile laboratory. 11 P-l'bdi dots of this higlr'puri'ty have been found very satisfatwry" for "use iiithe preparation of It'is toben'oted inbur iII p IoVed"Process a c0dolingcoil-s until the liquid that-theactlialcrystals-are not transferred to 1 lportlonim thi? crystalhzerwhas dropped to 28 "urea ace bra- "aiame for the -1'-em'ova1 of A Valve-then Opened the bQt'tOm of anq D thecrystalhzer and =-the mother liquor is "rials; ivhich aremore 'orllesstox'ic. It is like- I with suction "when them has Practically Wise to noted that no fsolve nts are neces-j aryao efiect gobderystallizatip M i The basis "of thisinventimi. resides the icausing theetemperature of. the mass in the cry'stallizer torise over a period of about 24 batch, suction isapplied at all times sothat any liquid material present is removed. The valve is nowclosed and the crystalsofalpha "crystallizing"Without agitation means of very highly egulated' ni'ethodofciooling t0 po'rtion d'rawn fofi byi 'simply "draining I and nal'ly by applying suction; "The tempera- .f-fafter vacuum" .,:fM01tnIcri 1ea1pha naphthylamine' with a a crystallizing' point'o f 44 to 45 C. is charged to 279 (This latter temperature is main:

rained *outyat' first by fgravity and finally -naphthylaminein thecry'stallizer are melted.

-- After a distillationfor cleansing purposes v ing point of 4850,01 above.

' the refined alphanaphthylamine has a meltf to " beta nitro f naphthalene" and alphafa'ndfibeta out in a manner similar to that described; in Example 1. The displacement of liquid in practice is performed by passing water I through the mass of the crystals increasing in is 110fabsolutely-nec ssary since the point i to fwliiclr the"systemfnust becooled around F room' or avera e; temperature; jandf that "the [cooling may be effectedbysimply allowing 0. and continuing at the temperature until practically all oily products are removed.

"It is to be understood that the temperature employ'edain the final cooling of either of these specificsystems, namely, alpha nitro --naphthalenebeta{ nitro "naphthalene; and

This "latter method is not to be" preferred. j "since thetime factorfentersfinhnd the variation "in 'temperat'ureflue to climatic" changes f'is"'not dependable. v I "f" Without limitifig ouqinvntion to'a'nyp'ar V t'i ciil'afprooedure; 'the" following examples vvvill'serve toillustrate ou'r ifieth'odin it'sipre xferred form. t x Eze I nentispresent in the system, as fori instance it luMlfi nffTciid *"Qjpha; nitro' naphthalene,"naphthalene,- it is necessary to cool correcrystallifzjing point- Cais charged int'othe1spoi-ldinglylower to'minimizethe loss-of the jcrystallizer. The cooling water= ig=1th n run desired product. *We' are also: aware; si nce thrbiig'h the-'fcoils at about 47 C. The 'tem-" the eutectic point of the-two systems' lies *perature*off th "cooling vvater isk "graduall c'los'e to ordinarytemperature," that purifica The crystallization and draining is carried, 10

" fi n 6 d y p air fi g -the temperatureof the Water up to about 50 ceased, vvater isagain circulated {in the coils 7 alpha naphthylamine-beta naphthylamine -may'be varied slightly tobring about simi V larresu'lts as above. In case a third compoto a point approaching the eutectic point to.

effect maximum crystallization in a' desirable physical form and the removal of the liquid impurities by gravity and positive displacement at as low a temperature as is possible.

It should be further noted that as an alternative procedure, practically. the entire system including the pure compound and the eutectic liquor may be frozen practically solid and the eutectic liquor be reformed by slowly bringing the temperature back to the eutectic point. T

Obviously the ideal practice for maximum recovery would be to draw oii" the liquid portion at the eutecticpoint. However, when there is a' third component present (say, naphthalene) the eutectic point of the mixture may be so low as to make it impractical to cool to that temperature. Thus if it were attempted to bring the temperature in Example I down to the actual eutectic temperature of the particularmixture used as starting material in this example, the cost of the cooling would probably be doubled or trebled wh le the additional percentage of alpha isomer recovered would be very small as compared to the percentage already recovered. Therefore it should be understood that by the term temperature slightly above the eutectic point as used in the claims is meant a temperature sufliciently above the eutectic point of the system to permit an economical recovery of the alpha component.

lVe are aware that numerous details of the process may be varied through a wide range without departing from fthe principles of this invention, and we, therefore, do not purpose limiting the patent granted hereon otherwise thannecessitated by the prior art.

We claim as our invention:

1. In the process of isolating a substantially pure alpha mono substituted naphthalene from a mixture containing principally alpha and beta isomerically substituted naphthalenes, the alpha component being present in excess of its proportion in a eutectic mixture oi the two components, the steps which comprise slowly bringing said mixture without agitation to a temperature slightly above the eutectic point and removing portions of the mixture that are liquid at that temperature. l o

2. In the process of isolating a substan tially pure alpha mono substituted naphthalene from a mixture containing principally alpha and beta isomericaliy substituted naphthalcnes, the alpha com ponent bein present in excess of its proportion in a eutectic mixture of the two components, the steps which comprise cooling the mixture from molten eutectic point and removing by gravity portions of the mixture liquid at that temperature.

4. In the process of isolating a substantially pure alpha mono substituted naphthalene from a mixture containing principally alpha and beta isomerically substituted naphthalenes, the alpha component being present in exc of its proportion in a eutectic mixture or the two components, the steps which comprise slowly bringing said mixture without agitation to a temperature slightly above the eutect c point, removing portions of the mixture that are liquid at that temperature,

graduallyheating the remaining mass to a temperature below the melting point under the conditions for obtaining the pure alpha substituted naphthalene and continuously renoving thosc portions of the mass that are liquid during the heating up stage.

5. In the pr cess of isolating a substan tially pure alpha mono substituted naphthalene from a mixture containing principally alpha and beta isomerically substituted naphthalenes, the alpha component being present in excess of its proportion in a eutectic mix ture of the two components, the steps which comprise slowly bringing said mixture without agitation to a temperature slightly above the eutectic point,-remov1ng portions of the mixture that are liquid at that temperature,

gradually heating the remaining mass to a temperature below the melting point under the conditions for obtaining the pure alpha substituted naphthalene and continuously displacing by means of a fluid medium which is substantially immiscible with the desired component under the conditions for obtaining those portions of the mass that are liquid during the heating up stage.-

(5. The process of isolating a substantially pure alpha mono substituted naphthalene from a crude mixture containing principally the alpha body and a relatively small proportion of the isomeric beta body, which comprises slowly cooling said mixture without agitation from a molten condition to a temperature slightly above the eutectic point, removing the then liquid portion by gravity, slowlyheating the remaining mass under the =conditions forobtaining'the alpha body and continuouslydisplacing by meansof a fluid mediumwhich is; substantially im-' ,inis'cib-le I with the desired component under I the conditions for obtaining those portions of the that are liquid. during theheating V :835: ii

to} a temperature below the; melting point upstagep V i, 7 The "process: 0t obtaining substantially pure alpha" na-phthylaniine; from acrude alpha naphthy'lannne massi containingsome beta i'ia'phthylamine, I the alpha component being present inexcess ofitsproportion in a eutectic mixture of the two components,

which comprises slowly cooling the inass from-the molten state without agitation to a temperature slightly above the eutectic point,-

removing those portions of the mass that are liquid at that temperature, slowly-heating lzlie remaining mass to atemperature slightly below the nieltingpoint under the conditionstor obtaining pure. alpha naphthylainineand, continuously removing those portions of the inassthatare liquid-during-the heating stage. 8. Theipro'cessj i of: obtaining substantially purealphanaphthylamine from crude alpha naphthylamine mass containing some beta naphthylamine', the "alpha component being present in excess. of its proportion in a eutectic mixture of the 'two components,

which comprises slowly cooling the mass Without agitation to a temperature of about 28 (1., removing by gravity those portions of the mass that are liquid at that temperafi'tllle, slowly heating the remaining mass to a temperature of about 46 0., and continuously removing by, ravity those portions of the mass that are ing stage. p p

9. The process of obtaining substantially pure alpha imphthylaniine from a crude alpha naphthylainine masscontaining some beta naphthylamine, the alpha component being present-in excess of its proportionin a eutectic mixture of the tWo components, which comprises gradually cooling the mass under regulated conditions but Without agitation from a molten condition to a temperature of about 28 0., removing those portions of the mass that are liquid at that temperature by draining and by applying suction to the mass, slowly heating the remaining mass to about 46 C. and simultaneously applyingsuction to the mass to remove liquid portions therefrom.

10. In the process of obtaining substantially pure alpha naphthylamine from a crude alpha naphthylainine mass containingsome beta naphthylamine, the alpha component being presentin excess of it proportion in'a' eutectic mixture of the two components, the steps which comprise gradually cooling the mass from the molten condition.

Without agitation to a temperature of about 28 C. and removing by gravity those poragitat'ion." I ,v

iquid during the heat-- 11. 4 In the process of obtaining "substan tially pure alpha naphthyla mine from a crude alpha naphthylamine inass containingsome beta. naphthylamine, the al ahacoin 'ponent being present in excess of its proportion in a eutectic mixture of thetwocompo i1ents, the steps which comprise gradually cooling the mass from the molten condition without agitation to a temperature slightly above the eutect c point and removing-by. gravity those" portions of the mass thata're liquid at that temperature, p i 12. The process of obtaining an alpha incno substituted naphthalene in" substan-T tially" pure'form'from a mixture composed ent in solid form in equilibrium with a liq- 'uidlphase largely separating the liquid phase from the solid by gravity and recover ing said sol-id alpha (component substantiallyjfreefrom adheringIliquidcontaining the undesired component, the entire process be ing carried "out-in the absence of mechanical 13.:T'he process ofbbttiini'iig;analphaQ mono-substituted naphthalene infsubst'an tiallfy pure form from a "mixture comprised mainly of alpha"fand beta isomeric'a'lly moire-sub tituted naphthalenes' and impuri this present ina higherthan eutectic proportion, which?comprisesthe steps of bringing the entire system; to equilibrium' at after'npera f tL1I'e at hlCll the greater part of the alpha component is present in solid phase whileallof the betacom' aonenflandimpuritiesd phase; separating gravitythe liquid phase hem the solid; and

present are" in' liqui recovering said solid phase-"substantially freeftr'o n any adhering liquid "containing" the'undesired componenhfthe' entire proce -dure"being cameaout under condit ons excluding mechanical agitation.

14. The process "bt lobtaining'f an alphah mono substituted naphthalene in substan tially pur form frbm a mixture' co inprised mainly of alphaand beta isom'erically-inonm I o substituted naphthalenes and impurit es and in vvhich theratio of the alpha"toflthe beta compjenentis higher than the eutectic 'rat1o,

whichacomprises the steps of bringing the en tire ystem to: equilibrium at' "a" temperature at which the system resolves tself nto two i hases, one of; said .pha'ses being llqllld and} aid 'in 'yvhich the" alpha component is tionsof the mass that are liquid at that tom-- peraturer biii containing," an; of; the" beta component and j --im u1-ines and the other of "saidphases-lbej g solid comprising a substantial quantity of the alpha component only, separating by gravity the liquid phase from the solid phase, the entire procedure being carried out under conditions excluding mechanical agitation whereby the solid phase is formed in a physical state favoring the separation of the liquid phase by gravity.

15. The process of obtaining substantially pure alpha nitro naphthalene from a crude alpha nitro naphthalene mass containing some beta nitro naphthalene, the alpha component being present in excess of its proportion in a eutectic mixt re of the two components, which comprises slowly cooling the mass from the molten state without agitation to a temperature slightly above the eutectic point, re noving those portions of the mass that are liquid at that temperature, slowly heating the remaining mass to a temperature below the melting point under the conditions obtaining of the pure alpha component and continuously removing hose portions of the mass that are liquid during the heating stage.

16. The process of obtaining substantially pure alpha nitro naphthalene from a crude alpha nitro naphthalene mass containing some beta nitro naphthalene, the alpha component being present in excess of its proportion in a eutectic mixture of the two components, which comprises slowly cooling the mass from the molten state without agitation to a temperature of about 20 0., removing those portions of the mass that are liquid at that temperature, slowly heating the remaining mass to a temperature of about 50 C. and continuously removing those portions of the mass that are liquid during the heating stage.

17. The process of obtaining substantially pure alpha nitro naphthalene from a crude alpha nitro naphthalene mass containing some beta nitro naphthalene, the alpha component being present in excess of its proportion in a eutectic mixture of the two components, which comp ises slowly cooling the mass from the molten state without agitation to a temperature slightly above the eutectic point, removing those portions of the mass that are liquid at that temperature by draining and by applying suction to the mass, slowly heating the remaining mass to a temperature below the melting point under the conditions for obtaining the pure alpha component and continuously removing those portions of the mass that are liquid during the heating stage.

18. The process of obtaining alpha mononitro naphthalene in substantially pure form from a mixture comprised mainly of alpha and beta mono'nitro naphthalenes and impurities and in which thealpha component is present in a higher than eutectic proportion, which comprises the steps of bringing the entire system to equilibrium at a temperature at which the greater part of the alpha component is present in solid phase while all of the beta component and impurities present are in liquid phase, separating by gravity the liquid phase from the solid, and recovering said solid phase substantially free from any adhering liquids containing the undesired components, the entire procedure being carried out under conditions excluding mechanical agitation.

19. The process of obtaining alpha naphthylamine in substantially pure form from a mixture comprised mainly of alpha and beta naphthylamines and impurities and in which the alpha component is present in higher than eutectic proportion, which comprises the steps of bringing the entire system to equilibrium at a temperature at which the greater part of the alpha component is present in solid phase while all of the beta component and impurities present are in liquid phase, separating by gravity the liquid phase from the solid, and recovering said solid phase substantially free from any adhering liquids containing the undesired components, the entire procedure being carried out under conditions excluding mechanical agitation.

In testimony whereof we have hereunto subscribed our names at Carrollville, Milwaukee County, Wisconsin.

HENRY J. VVEILAND. IVAN GUBELMANN.

lie 

